Rectifier protective system



Sept. 21, 1937. H. WINOGRAD RECTIFIER PROTECTIVE SYSTEM Filed Aug. 21, 1933 2 Sheets-Sheet 1 Sept. 21, 1937.

H. WINOGRAD RECTIFIER PROTECTIVE SYSTEM Filed Aug. 21, 1933 2 Sheets-Sheet 2 Patented Sept. 21, 1937 RECTIFIER PROTECTIVE SYSTEM Harold Winograd, Milwaukee, Wis., assignor to Allis-Chalmers Manufacturing Company, Milwaukee, Wis., a corporation of Delaware Application August 21, 1933, Serial No. 685,973

20 Claims.

This invention relates to improvements in protective systems and more particularly to systems for interrupting fault currents flowing through an electron discharge device and for thereafter reestablishing the flow of normal current therethrough.

In systems employing electron discharge devices such as an electric valve, upon occurrence of any disturbance resulting in an abnormal flow of current through such valve, it is generally advantageous to interrupt such flow of current by the action of discharge controlling means of suitable nature provided within the valve itself. In this way interruption of the flow of current is obtained more rapidly than by means of mechanical circuit interrupting devices. The action of such discharge controlling means however sometimes fails to operate due to the abnormal temperature or pressure conditions in the valve during the flow of excessive current therethrough so that it is necessary to provide, in the circuit of the valve, some circuit interrupting means externally of the valve and operable to interrupt the flow of excessive current when such interruption is not caused by means of the discharge controlling means. It is then desirable to so control the circuit interrupting means that such external means will operate only when the discharge controlling means have failed to entirely interrupt the flow of current and even if the current, although not entirely interrupted, has been reduced to a value which may be considerably lower than the maximum normal value thereof.

It is therefore among the objects of the present invention to provide a protective system for electron discharge devices by which the device is made non-conductive upon occurrence of a disturbance in the system.

Another object of the present invention is to provide a protective system for electron discharge devices by which circuit interrupting means, external to the device, interrupt any fault currents which the device itself may fail to interrupt.

Another object of the present invention is to provide a protective system for electron discharge devices by which the responsiveness of the means for interrupting the circuit of the device is varied when the device is caused to interrupt the flow of current therethrough.

Objects and advantages other than those above set forth will be apparent to those skilled in the art upon consideration of the following descripings in which:

Fig. 1 diagrammatically illustrates one embodiment of the present invention applied to the control of an alternating current rectifier protected by relays, the setting of which is changed by a relay also impressing a negative potential on the control electrodes of the device upon occurrence of a disturbance;

Fig. 2 diagrammatically illustrates a portion of a modified embodiment of the present invention in which the relay impressing a negative potential on the control electrodes of the device is replaced by an auxiliary electric valve;

Fig. 3 diagrammatically illustrates another modified embodiment of the present invention in which the voltage of the direct current line is maintained constant during normal operation and in which the flow of current is progressively reestablished after interruption of fault current;

and

Fig. 4 diagrammatically illustrates a portion of a further modified embodiment of the present invention in which the reestablishment of normal current is controlled by means of an auxiliary electric valve.

Referring more particularly to the drawings by characters of reference, reference ,numeral 6 designates an alternating current line of any desired voltage at any frequency and of any number of phases, herein represented as a three phase line. It is assumed that alternating current obtained from line 6 is to be converted into direct current to be supplied to a direct current line having a positive conductor 8 and a negative conductor 7.

To obtain this effect, line 6 is conthe sake of brevity.

Rectifier I4 is provided with a cathode 18 connected with conductor 8. The potential of cathode 16 will herein be used as datum and all potentials will be referred thereto r unless otherwise stated. Any source of electromotive force having one terminal thereof connected with cathode IE will therefore have the other terminal thereof at a such electromotive potential equal to force and such source will then become a source of potential for any circuit connected therewith. Rectifier M is provided with the usual discharge igniting and maintaining means which do not materially affect the operation of the present system and are therefore not shown. The flow of current through anodes I3 is controlled by suitable discharge controlling means such as control electrodes Il each connected through a resistor l8 and contacts of a relay 89 with a source of potential such as a battery it having one terminal thereof connected with cathode it.

During normal operation of rectifier M, control electrodes I! receive a positive potential from battery 2! and, upon operation of relay l9 due to the occurrence of a disturbance, control electrodes ii receive a negative potential from battery 2! for the purpose of causing the fiow of current through rectifier M to be interrupted as is well known. Circuit breaker Q is provided with a trip coil 22 which is connected to be energized from any suitable source such as battery 2| through the contacts of relays 23, 24 and 26. The latter relays are energized with current in relation with the magnitude of the current flowing through the winding H and through rectifier it by means of current transformers 21, 28 and 29 inserted in the connections between circuit breaker 9 and winding l I. During normal operation of rectifier M, the coils of relays 23, 24 and 26 are shunted by suitable impedances such as resistors 3!, '32 and 33 through the contacts of a relay 3d. The coil of relay 34 may be energized from a suitable source such as battery 2i through contacts 36 of relay I9. The coil of relay I9 is energized in relation with the flow of current through winding H by any suitable connection such as by insertion of such coil in series with the coil of relay 26. Relay I9 is of any suitable type capable of attracting the armature thereof in the shortest possible time and of releasing such armature with an adjustable time delay. Relay St is also preferably of a type attracting the armature thereof in the least possible time, but the speed of release of such armature is immaterial. Relays 23, 2d and 2% are preferably of a comparatively slow acting type adjusted to be responsive to the flow of overload currents even of small magnitude through current transformers 21, 28 and 29 as long as the coils of the relays are shunted by the re sisters 35, 32 and 33. Upon opening of the connections of such resistors by relay 3d, relays 23, 2 and 26 will then become responsive to the flow of current of any magnitude in excess of the magnetizing current of transformer ll, l2 to thereby become responsive to the flow of current of any magnitude through rectifier l4. Relay i9 is so adjusted as to be responsive only to the flowof currents of large magnitudes resulting from abnormal conditions such as a short circuit in line I, 8 or a backfire in rectifier I l. Cathode i6 is preferably connected with conductor 8 through a circuit breaker 3i preferably operable to open when released by a polarized latch 38 responsive only to the flow of current from conductor 8 towards cathode 16, to thereby interrupt the reverse current supplied by any sources connected with line i, 8 to rectifier 54 upon occurrence of a backfire therein. Circuit breaker 3? is preferably of the self reclosing type operated by means of a closing coil 35 energized by rectifier M through auxiliary contacts 40 of the breaker and through a control switch 45.

As a result of such connections, circuit breaker 9 controls the fiow of current from line 6 to line i, 8 by way of valve or rectifier I4. Relays 23, 24 and 26 are operable to be responsive to the flow of currents of any magnitude through rectifier M and, therefore, to an operating condition of the system, to control the opening operation of circuit breaker 9 upon. failure of control electrodes H to completely prevent the fiow of current entirely through rectifier M. The adjustment of relays 23, 2t and 26 is varied to render such relays responsive to only abnormal flows of current through rectifier 14 by means of resistors 3!, 32 and 33 and by means of relay 35 which is controlled by relay l9. Relay l9, which is responsive to the flow of excessive currents through the system and, therefore, responsive to abnormal operating conditions of such system, is operable to control the action of control electrodes H by negatively energizing such control electrodes to cause cessation of the fiow of current from line 5 to line I, 8 by way of rectifier i l and to render resistors 31, 32 and 33 ineffective, thereby causing relays 23, 24 and 26 to become responsive to the flow of any residual current through rectifier M.

In operation, line B being energized, circuit breaker 9 and switch 65 being closed, and the discharge being ignited in rectifier M, a current fiows from rectifier M through the operating coil of circuit breaker 3? which closes and causes fiow of current through rectifier M to line 1, 8 as is well known in the art. In the embodiment illustrated in Fig. 1, control electrodes ll are positively energized from battery 2! only to facilitate the transfer of the discharge from one anode to another, such action being particularly useful when the load on the. rectifier is low. During normal operation, the currents flowing through the coils of relays i9, 23, 24 and 26 are insufficient to cause any of such relays to operate.

Upon occurrence of a disturbance such as a short circuit in line i, S or a backfire in rectifier l i, an excessive fiow of current occurs from line 6 through current transformers 21, 28 and 29, windings H and i2 and rectifier M, such flow of current also continuing through line I, 8 if the disturbance is a short circuit in such line. As a result of such flow of current, the coil of relay l9 receives ,a large amount of current from current transformer 2.9 and instantly attracts the armature thereof, thereby reversing the connections of battery 20 with control electrodes ill and cathode 56. Control electrodes negatively energized prevent the transfer of the discharge to any of the anodes not carrying current at the instant considered, and the fiow of current through rectifier M ceases when the anodes carrying current at the time of the disturbance cease to be positive with respect to cathode l6. Relay l9 also closes contacts 36, thereby energizing the coil of relay 34 which opens the circuit of resistors SI, 32 and 33. The

coils of relays 23, 2d and 26 then receive the,

entire currents of current transformers Z1, 28 and 29. Assuming that the extinguishing action of control electrodes ll resulted in a complete interruption of the flow of current through rectifier M, such interruption will have been completed before relays 23, 24 and 26 close the contacts thereof and such relays then receive only a current corresponding to themagnetizing current of transformer ll, 62 and do not attract their armatures. After a predetermined time delay,

l'i thus being 3 relay l9 returns to the position shown, thereby returning the system to the originaloperating condition thereof. If the disturbance was a backfire in rectifier |4, thesystem may generally continue to operate normally. If the disturbance was a short circuit in line 1, 8,'such short circuit must of course be removed by suitable circuit breakers (not shown) inserted in line I, 8 or in any feeders supplied thereby. If line 8 is connected with sources of current other than rectifier M or if the loads connected therewith are operable to function as sources of current, upon occurrence of a backfire in rectifier l4, current will flow from conductor 8 through rectifier 4 and winding |2 to conductor 1, and such current will be interrupted by circuit breaker 3'| irrespective of its magnitude. Upon restoration of rectifier M to the operating condition thereof, coil 35 becomes reenergized and circuit breaker 31 reconnects cathode IS with conductor 8.

If some or all of control electrodes fail to prevent further flow of current through the associated anodes for any reason, current will continue to fiow through rectifier |4. If only one or a few of control electrodes H are inoperative, the average magnitude of such current may be smaller than the normal current of rectifier 4. Relay 34 having operated as described above, the flow of such residual current will however cause sufficient current to flow through the coils of relays 23, 24 and 26 to cause at least one of such relays to operate and to connect trip coil 22 with battery 2|, thereby causing circuit breaker 8 to open. Such opening of circuit breaker 9 is an indication of the defective condition of control electrodes l1 and fiow of current through the system therefore preferably remains interrupted.

If a short circuit or a ground fault occurs in either winding II or winding I2, such fault will generally result in a flow of excessive current sufiicient to cause one of relays 23, 24 or 26 to operate, even when relay 34 is in the position shown, to thereby cause energization of trip coil 22 and opening of circuit breaker 8. If the fiow of current resulting from such fault is sufficiently great, relays l9 and 34 will also operate with the ultimate result of interrupting the circuit.

In the embodiment illustrated in Fig. 2, battery 2| is permanently connected with control electrodes I! through resistors l8 and through a single resistor 38, the purpose of which will appear hereinafter. Negative potential for control electrodes I1 is then supplied by means of a second battery 4| connected with resistors I8 through additional contacts 42 controlled by relay 34 and through the coil of relay 34 and through a discontinuously controllable auxiliary discharge device herein shown as a valve 43 of the vapor type. In the present embodiment, relay 34 is again of the instantly operating type causing instant opening of the contact thereof with the exception of contacts 42 which are opened only after a predetermined time delay. Valve 43 is provided with an anode connected with resistors l8 and also connected with conductor 8 through another resistor 48; and with a cathode connected with the coil of relay 34. The operation of valve 43 is controlled by means of a control electrode connected with the cathode of the valve through a resistor 44, through a bias battery 46 and through another resistor 41 receiving the current of current transformer 29 due to the connection of such resistor similarly to the connection of the coil of relay IQ of Fig. 1.

In the present embodiment the elements common to the embodiment illustrated in Fig. 1 retain their original functions except that battery 2| controls the action of control electrodes only during normal operation of rectifier |4. Battery 4| is operable to overcome the action of battery 2| to cause cessation of the fiow of current through rectifier 4.

The normal operation of the system illustrated in Fig. 2 is similar to that of the system illustrated in Fig, 1. During such operation, the control electrode of valve 43 receives an alternating voltage component with respect to the associate cathode from resistor 41, and also receives a negative direct current voltage component, which is higher than the alternating component, from battery 46 so that such control electrode is always negative with respect to the cathode of the valve and the valve remains non-conductive. Upon occurrence of a short circuit in line 1, 8 or of a backfire in rectifier M, an excessive current flows through current transformers 21, 28 and 29, resistor 41 and the coils of relays 23, 24 and 26. The voltage drop in resistor 41 is thereby increased to a value such that such drop over comes the voltage of battery 46 once per cycle, thereby causing valve 43 to become conductive. Such valve thereafter remains conductive as a result of the flow of current therethrough from battery 4| through conductor 8, resistor 48, valve 43, coil of relay 34 and contacts 42. The negative potential of battery 4| is applied to control electrodes |1 through resistors 8, thereby overcoming the action of battery 2|, the potential of which then appears as a voltage drop in resistor 38. The action of control electrodes l1 and of relays 34, 23, 24 and 26 is then the same in the embodiments illustrated in Figs. 1 and 2. In addition, relay 34 having operated causes opening of contacts 42 after a predetermined time delay to cause interruption of the flow of current through valve 43 after the flow of current through rectifier M has been interrupted either by the action of control electrodes H or by opening of circuit breaker 8 as above described. At such time the control electrode of valve 43 is again constantly negative with respect to the cathode of the valve and regains control of the valve upon interruption of the fiow of current there through,

In the embodiment illustrated in Fig. 3, control electrodes ii are energized by alternating voltage components by means of the star connected secondary winding 49 of a control transformer having a primary winding 50 energized from line 6. The neutral point of winding 49 is connected through contacts of a relay 5| with the movable tap of a resistor 52 constituting a portion of a regulator generally designated by 53. Resistor 52 is connected with line 1 through a rheostat 54 and with line 8 through resistor 56 thereby constituting an adjustable voltage divider impressing, on control electrodes IT, a negative potential equal to a portion of the voltage of line 8. Regulator53 operates under the action of a torque producing element 51 of any suitable type having the windings thereof energized from line I, 8 through a rheostat 58. Element 51 acts against a spring 59 to vary the position of the tap of resistor 52. In the present embodiment, relay 5| replaces relay IQ of the embodiment illustrated in Fig. 1 and the operation of such relay results in connection of the neutral point of windings 49 between a resistor 6| connected with line and a capacitor 62 connected with line 8. Capacitor 62 may be shunted by a rheostat 53 to control the rate of discharge thereof when line l, 2 is deenergized. Relay 5i is provided with a holding coil connected between the neutral point of winding 49 and the tap of resistor 52through a rheostat 64. In the present embodiment, current transformer 28, relay 24 and resistor 32, of the embodiment illustrated in Fig. l, are omitted and resistors 3i and 33 shunt not only the coils of relays 23 and 25 respectively but also the coil of a relay 59 receiving the combined currents of coils of relays 24 and 26 and operating in the same manner as relay 34 of Fig. 1. Eattery 2! not being used in the present embodiment, a separate source such as battery 51 is provided for the purpose of energizing trip coil 22 of circuit breaker 9.

In the present embodiment, relay (it performs the functions performed by relay 34 in the preceding embodiment-s. During normal operation of rectifier Hi, control electrodes H are controlled by regulator 53 and transformer 49, 59 to regulate the flow of current between line 6 and line l, 8 by way of rectifier i l. Relay 5! performs the same functions as relay B9 of the preceding embodiments and also connects the control electrodes l'i with capacitor 62 to negatively energize such control electrodes and. thereby overcome the action of transformer 69, 59, and momentarily interrupt the flow of current through rectifier l4. Relay 55 also cooperates with capacitor 62 and transformer 49, 50 to progressively reestablish the flow of current through rectifier M, as will appear hereinafter.

During normal operation of rectifier M, relay 5! impresses, on the control electrodes ll, potential including the negative direct current potential component of resistors 52 and 56. Upon occurrence of a disturbance, relay 5! substitutes for such direct current potential, the negative potential of capacitor 62 to cause interruption or the flow of current through rectifier M, and thereafter restores the application of the negative potential component on the control electrodes when such component and the potential of capacitor 62 diifer by less than a predetermined amount. Capacitor 62 constitutes energy storage means connected with cathode l5 and is negatively charged by means of line I, 8 through resistor Resistor 5G and rheostats 63 and (it gradually dissipate the charge of capacitor 62 after interruption of the flow of current through rectifier id and thus cause such flow of current to be progressively reestablished.

During normal operation, control electrodes ll receive, from transformer 59, 59 and resistors 56 and 52, unsymmetrical alternating voltages such that each control electrode becomes positive when the associated anodes have become positive. the times of positive energization of the control electrodes being regulated by'regulator 53 in a manner such that the voltage of line i, 8 remains constant if the torque of spring 59 is constant or varies according to a predetermined law of variation depending upon the characteristic of spring 59. During such operation, the current flowing through the coils of relays 5t, 66, 23 and 26 are insufficient to cause such relays to operate.

Upon occurrence of a disturbance such as a short circuit in line 1, 8 or a backfire in rectifier l4, either current transformer 21 or 29 or both current transformers carry excessive currents which flow though the coils of relays 23, 26, 5! and 6%. Relay 5! disconnects the neutral point of winding 69 from the tap of resistor 52 and reconnects such neutral point with capacitor 62,

thereby impressing, on control electrodes a negative potential equal to a portion of the normal voltage of line I, 8 by which voltage portion capacitor 62 was charged. Such negative voltage is, so chosen as to overcome the smaller voltages of winding 49 and control electrodes H are then all maintained negative to cause interruption of the flow of current through rectifier I4. Relay 56 also operates to open the connections of resistors 3i and 33 thereby rendering relays 23, 26 and 66 responsive to the flow of any residual current flowing through rectifier I4 and causing opening of circuit breaker 9 upon faulty operation of control electrodes ll. Assuming that control electrodes I! have interrupted the flow of current, regulator 53 instantly returns to the position shown due to the action of spring 59. The armature of relay 5! then remains attracted by theholding coil of relay 5| which receives current from capacitor 62 through resistor 56, the tap of resistor 52 and rheostat 64. Capacitor 62 thus gradually discharges at a rate which may be adjusted by means of rheostat 63 providing another discharge path for capacitor 62. In general, resistor BI is chosen of high ohmic value so as to permit charging and discharging therethrough of capacitor 62 at a very slow rate. The flow of current through rectifier M remains interrupted as long as the potential of capacitor 62 remains larger than the peak value of the voltages of winding 49. After a predetermined period oftime depending upon the adjustment of rheostats 63 and 64, the potential of capacitor 62 decreases below the peak value of the voltages of winding 49 so that control electrodes I! again become positively energized but at a later part of the voltage cycle of line 5 than during normal operation to thereby permit initiation of the flow of current through rectifier I4 at a reduced voltage.

, If circuit breaker 31 has opened, coil 35 is then reenergized so that circuit breaker 31 recloses. Line I, 8 is then reenergized at such reduced voltage which gradually increases in response to the continued decrease of potential of capacitor 92 due to the gradual advance of the times of energization of the control electrodes during the voltage cycle of line 6. The flow of current is also reestablished through resistors 56 and 52 and rheostat 54 thereby producing an increasing negative potential drop across resistor 56. The holding coil of relay 5|, which is energized at the difference between the terminal voltages of resistor 56 and of-capacitor 62, thereby receives a gradually decreasing amount of current and, when such current decreases below a predetermined value, relay 5! returns to the position shown to reestablish the normal connections of the system. The flow of current is then reestablished at the full value thereof determined by the load connected with line I, 8. i

In the embodiment illustrated in Fig. 4,-the holding coil of relay 5| is connected through a battery 99 with the anode of a continuously controllable electron discharge device such as a valve 58 having the cathode thereof connected with capacitor 62. Valve 68 is provided with a control electrode connected with the tap of resistor 52 through a resistor 12 and a bias battery 'H. Relay 5! is provided with an additional pair of contacts completing the circuit of the holding coil thereof upon operation of the relay.

As in the embodiment illustrated in Fig. 3, operation of relay 5| in response to the occurrence of a disturbance causes connection of the neutral point .of winding 49 with capacitor 82 to cause interruption of the flow of current through rectifier I l. The tap of resistor 52 is then at the potential of cathode 15 so that the control electrode of valve 68 is highly positive with respect to the cathode of such valve and the valve becomes conductive thereby permitting flow of current from battery 69 through valve 68 and the holding coil of relay which retains the armature thereof in the attracted position. Upon suflicient decrease of the potential of capacitor 62, the fiow of current through rectifier I4 is progressively reestablished as explained above and the tap of resistor 52 is brought to an increasingly negative potential. When such potential reaches a predetermined value, the control electrode of valve 68 causes the flow of current through such valve to decrease to such extent that the holding coil of relay 5| no longer maintains the armature of the relay attracted and relay 5| returns to the position shown to complete the restoration of the flow of current through rectifier 14.

Although but a few embodiments of the present invention have been illustrated and described, it will be apparent to those skilled in the art that various changes and modifications may be made therein without departing from the spirit of the invention or from the scope of the appended claims.

It is claimed and desired to secure by Letters Patent:

1. In an electron discharge device protective system, an electric current supply circuit, electron discharge means connected with said circuit, an electric current output circuit connected with said discharge means, means controlling the connection of said supply circuit with said output circuit by way of said discharge means, discharge controlling means for said discharge means, means for controlling the action of said discharge controlling means to cause cessation of the flow of current through said discharge means, and means operable responsive to the flow of current of value not greater than the value of the flow of current through said discharge means during normal operation of the system for causing operation of the second said means upon failure of said discharge controlling means to completely prevent theflow of current through said discharge means.

2. In an electron discharge device protective system, an electric current supply circuit, electron discharge means connected with said circuit, an electric current output circuit connected with said discharge means, means controlling the connection of said supply circuit with said output circuit by way of said discharge means, discharge controlling means for said discharge means, means responsive to an operating condition of said system for controlling the action of said discharge controlling means to cause cessation of the flow of current through said discharge means, and means operable responsive to the flow of current of value not greater than the value of the flow of current through said discharge means during normal operation of the system for causing operation of the second said means upon failure of said discharge controlling means to completely prevent the flow of current through said discharge means.

3. In an electron discharge device protective system, an electric current supply circuit, electron discharge means connected with said circuit, an electric current output circuit connected with said discharge means, means controlling the connection of said supply circuit with said output circuit by Way of said discharge means, discharge controlling means for said discharge means, means responsive to an abnormal condition of said system for controlling the action of said discharge controlling means to cause cessation of the flow of current through said discharge means, and means operable responsive to the flow of current of value not greater than the value of the flow of current through said discharge means during normal operation of the system for causing operation of the second said means upon failure of said discharge controlling means to completely prevent the flow of current through said discharge means.

4. In an electron discharge device protective system, an electric current supply circuit, electron discharge means connected with said circuit, an electric current output circuit connected with said discharge means, means controlling the connection of said supply circuit with said output circuit by way of said discharge means, discharge controlling means for said discharge means, means responsive to a flow of excessive current through said system for controlling the action of said discharge controlling means to cause cessation of the flow of current through said discharge means, and means operable responsive to the flow of current of value not greater than the value of the flow of current through said discharge means during normal operation of the system for causing operation of the second said means upon failure of said discharge controlling means to completely prevent the fiow of current momentarily through said discharge means.

5. In an electron discharge device protective system, an electric current supply circuit, electron discharge means connected with said circuit, an electric current output circuit connected with said discharge means, means controlling the connection of said supply circuit with said output circuit by way of said discharge means, discharge controlling means for said discharge means, means for controlling the action of said discharge controlling means to cause cessation of the flow of current through said discharge means, means for controlling the operation of the second said means, and means controlled by the fourth said means for varying the adjustment of the last said means.

6. In an electron discharge device protective system, an electric current supply circuit, electron discharge means connected with said circuit, an electric current output circuit connected with said discharge means, means controlling the connection of said supply circuit with said output circuit by way of said discharge means, discharge controlling means for said discharge means, means for controlling the action of said discharge controlling means to cause cessation of the flow of current through said discharge means, means responsive to an operating condition of said system for controlling the operation of the second said means, and means for varying the responsiveness of the last said means upon operation of the fourth said means.

7. In an electron discharge device protective system, an electric current supply circuit, electron discharge means connected with said circuit, an electric current output circuit connected with said discharge means, means controlling the N connection of said supply circuit with said outputcircuit by way of said discharge means, discharge controlling means for said discharge means, means for controlling the action of said discharge controlling means during normal operation of said discharge means, means for overcoming the action of the last said means to cause cessation of the flow of current through said discharge means, and means operable responsive to flow of any residual current through said electron discharge means for causing operation of the second said means upon failure of said discharge controlling means to completely prevent the flow of current momentarily through said discharge means.

8. In an electron discharge device protective system, an electric current supply circuit, electron discharge means connected with said circuit, an electric current output circuit connected with said discharge means, means controlling the connection of said supply circuit with said output circuit by way of said discharge means, discharge controlling means for said discharge means, means for controlling the action of said discharge controlling means'to regulate the flow of current through said discharge means, means for overcoming the action of the last said means to cause cessation of the flow of current through said discharge means, and means operable responsive to flow of any residual current through said electron discharge means for causing operation of the second said means upon failure of said discharge controlling means to completely prevent the flow of current momentarily through said discharge means.

9. In an electron discharge device protective system, an electric current supply circuit, electron discharge means connected with said circuit, an electric current output circuit connected with said discharge means, means controlling the connection of said supply circuit with said output circuit by way of said discharge means, discharge controlling means for said discharge means, means for controlling the action of said discharge controlling means to cause cessation of the flow of current through said discharge means, means for causing operation of the second said means upon failure of said discharge controlling means to completely prevent the flow of current momentarily through said discharge means, and automatic means for progressively restoring the flow of current after the momentary interruption thereof.

10. In an electron discharge device protective system, an electric current supply circuit, an electric valve having an anode with an associated control electrode and a cathode and being connected with said circuit, an electric current output circuit connected with said valve, a circuit breaker controlling the connection of said supply circuit with said output circuit by way of said valve, relay means for controlling the opening operation of said circuit breaker, and means operable to negatively energize said control electrode with respect to said cathode to cause cessation of the flow of current between said circuits by way of said valve and to cause the said relay means to'then become responsive to flow of any residual current through said valve. v

11. In an electron discharge device protective system, an electric current supply circuit, an electric valve having an anode with an associated control electrode and a cathode and being connected with said circuit, an electric current output circuit connected with said valve, a circuit breaker controllingthe connection of said supply circuit with said output circuit by way of said'valve, relay means responsive to the flow of current of any magnitude through said valve for controlling the opening operation of said circuit breaker, and means normally rendering said re lay means responsive to only abnormal flow of current through said valve and negatively energiz ing said control electrode with respect to said cathode to cause cessation of the flow of current between said circuit by way of said valve and to then render the last said means ineffective.

12. In an electron discharge device protective system, an electric current supply circuit, an electric valve having an anode with an associated control electrode and a cathode and being connected with said circuit, an electric current output circuit connected with said valve, electric energy storage means connected with said cathode, means for supplying a negative charge to said storage means, and means for impressing on said control electrode a potential including a direct current potential component negative with respect to the potential of said cathode during normal operation of said valve and to substitute the potential of said storage means for the said negative potential component to cause interruption of the flow of current through said valve.

13. In an electron'discharge device protective system, an electric current supply circuit, an electric valve having an anode with an associated control electrode and a cathode and being connected with said circuit, an electric current output circuit connected with said valve, electric energy storage means connected with said cathode, means for supplying a negative charge to said storage means, means for impressing on said control electrode .a potential including a direct current potential component negative with respect to the potential of said cathode during normal operation of said valve and to substitute the potential of said storage means for the said negative potential component to cause interruption of the flow of current through said valve, and means for gradually dissipating the charge of said storage means for causing the flow of current through said discharge means to be progressively reestablished.

14. In an electron discharge device protective system, an electric current supply circuit, an electric valve having an anode with an associated control electrode and a cathode and being connected with said circuit, an electric current output circuit connected with said valve, electric energy storage means connected with said cathode, means for supplying a negative charge to said storage means, means for impressing'on said control electrode a potential including" a direct current potential componentnegative with respect to the potential of said cathode during normal operation of said valve and to substitute the potential of said storage means for the said negative potential component to cause in terruption of the flow of current through said valve, means for gradually dissipating the charge of said storage means for causing the flow of current through said discharge means to be progressively reestablished, and means for automatically restoring the application of said direct current potential to said control electrode when such potential and the potential of said storage means become different by less than a predetermined amount.

15. In combination, an electric circuit subject to a flow of current of variable magnitude,

means serially connected in said circuit responsive to the magnitude of said flow of current, and a shunt circuit connected across said means including contacts of a relay for opening said shunt circuit in response to increase of the magnitude of said flow of current above a predetermined value to modify the responsiveness of the said means.

16. In combination, an electric circuit subject to a flow of current of variable magnitude, a relay connected in parallel with a shunt circuit and serially connected in said electric circuit to operate in response to variations of the magnitude of said flow of current, and a second relay responsive to the magnitude of said flow of current for opening said shunt circuit when said flow of current exceeds a predetermined value.

1'7. In an electron discharge device protective system, an electric current supply circuit, electron discharge means connected with said circuit, an electric current output circuit connected with said discharge means, means controlling the connection of said supply circuit with said output circuit by way of said discharge means, discharge controlling means for said discharge means, means for controlling the action of said discharge controlling means to cause cessation of the flow of current through said discharge means, and means operable responsive to the flow of current through said electron discharge means only upon said current exceeding a predetermined value above zero before operation of the fourth said means and only upon said current exceeding another value above zero after operation of the fourth said means for causing operation of the second said means upon failure of said discharge controlling means to completely prevent the flow of current through said discharge means.

18. In an electron discharge device protective system, an electric current supply circuit, electron discharge means connected with said circuit, an electric current output circuit connected with said discharge means, means controlling the connection of said supply circuit with said output circuit by way of said discharge means, discharge controlling means for said discharge means, means for controlling the action of said discharge controlling means to cause cessation of the flow of current through said discharge means, and means operable responsive to the flow of current through said electron discharge means only upon said current exceeding a predetermined value above zero before operation of the fourth said means and only upon said current exceeding another value above zero and lower than said predetermined value after operation of the fourth said means for causing operation of the second said means upon failure of said discharge controlling means to completely prevent the flow of current through said discharge means.

19. In an electron discharge device protective system, an electric current supply circuit, electron discharge means connected with said circuit, an electric current output circuit connected With said discharge means, means controlling the connection of said supply circuit with said output circuit by way of said discharge means, discharge controlling means for said discharge means, means for controlling the action of said discharge controlling means to cause cessation of the flow of current through said discharge means, and means operable responsive to the flow of current through said electron discharge device upon said current being maintained at any value including normal operating values thereof after operation of the fourth said means and before operation of the second said means for causing operation of the second said means upon failure of said discharge controlling means to completely prevent the flow of current through said discharge means.

20. In an electron discharge device protective system, an electric current supply circuit, electron discharge means connected with said circuit, an electric current output circuit connected with said discharge means, means controlling the connection of said supply circuit with said output circuit by way of said discharge means, discharge controlling means for said discharge means, means for controlling the action of said discharge controlling means to cause cessation of the flow of current through said discharge means, and means operable less rapidly than the fourth said means and responsive only to said flow of excessive current through said system before operation of the fourth said means and to the presence of any flow of current through said system after operation of the fourth said means for causing operation of the second said means upon failure of said discharge controlling means to completely prevent the flow of current through said discharge means.

HAROLD WINOGRAD. 

